Alloy



atenied July 14, 1936 ALLOY James M. Lohr, Morristown, N. 1., assignor tol Driver-Harris Company, Harrison, N. 1., a corporation of New Jersey No Drawing. Application July 27, 1935,

Serial No. 33.580 1 4 Claims; (Cl. -128) This invention relates to alloys and more particularly to alloys for electrical resistance units.

In the patent to Hunter No. 2,005,423, granted June 18, 1935 there is disclosed the addition of calcium to nickel-chromium and nickel-chromium-iron alloys in such amounts that a residue of calcium remains in the alloy. Likewise, in my prior Patents Nos. 2,005,430, 2,005,431, 2,005,432 and 2,005,433, granted June 18, 1935, the addition of molybdenum, zirconium and calcium and calcium, zirconium and aluminum to nickelchromium and nickel-chromium-iron alloys is disclosed. The alloys disclosed in said patents are particularly useful in resistance units that are subjected to high temperatures such as heating elements. Where a resistance unit is to be used at lower temperatures, such as in rheostats, a less expensive alloy containing less nickel and more iron is frequently used. I have found that theuseful life of such alloys can be increased by the addition of various deoxidizers in such amounts that a residue of the deoxidizer or deoxidizers remains in the alloy. Thus calcium and zirconium may be added to such alloys in such amounts that from .01 to .20 percent of calcium and .01 to .50 percent of zirconium remain in the alloy.

The alloys to which the present invention relates are ones containing more nickel than chromium and in which the range of the metals, nickel, chromium and iron, extends from 20 to 50 percent nickel, 5 to 25 percent chromium and the balance iron. In preparing alloys contain-' ing calcium and zirconium, the quantities of calcium and zirconium are subtracted from the iron content. Thus in preparing alloys in the ranges stated above, the final alloys will contain from 20 to 50 percent nickel, 5 to 25 percent chromium, .01 to .20 percent calcium, .01 to .50 percent zirconium and the balance iron.

Manganese and silicon may also be added to the alloy and are preferably used within the following limits:

Percent Manganese .01 to 2.0 Silic .01 to 2.0

The preferred proportions of the alloying elements are as follows:

v Percent Nickel 35 Chrhminm 15 5 Calcium .03 Zirconium .03 to .25 Iron Balance In this alloy, a proportion of zirconium near the 10 lower limit is preferred.

Nickel-chromium-iron alloys of the character set forth above containing calcium and zirconium within the limits set forth have been found by tests to give a greatly increased period of life 15 over similar alloys without the calcium and zirconium additions. For the purpose of determining the life of such alloys at high temperatures,

I have tested them by the method of test outlined in Tentative accelerated life test for metallic materials for electrical heating of the 20 American Society for Testing Materials described in vol'. 29 of the Proceedings of the Thirty-Second Annual Meeting of the American Society for Testing Materials" beginning on page 613. The method is substantially as follows:

A sample of the wire to be tested, free from kinks, approximately twelve inches long and of about .025 inch diameter, is mounted vertically on the test board, the upper end being held in position by means of a suitable binding post. A 10 gram weight is attached to the lower end oi. the specimen. A short piece of wire is attached to the 10 gram weight and projects downward into a cup of mercury where it may move freely up and down. A rheostat and an interrupter are connected in series with the specimen to the power supply. The test is run on constant temperature at a standard temperature chosen for the alloy under consideration for the first twentyfour hours. Thereafter it is run on constant voltage to the burnout. The life in hours up to a 10 percent increase in resistance is known as useful life while the life to the burnout is known as total life. Throughout the test the power is on two minutes and oil! two minutes. This is accomplished'by means of an interrupter.

In testing the alloys of my invention according to the above described method, a reference sample composed of 35 percent nickel, 15 percent chromium and balance iron and having no calcium or zirconium addition was used. The life of this sample is considered as percent and the useful life of samples containing calcium V and zirconium within the ranges stated was cal- 5 culated therefrom. The useful life of such samples varied from 195 percent to 685 percent of the standard.

In the alloys referred to herein small amounts of phosphorous and sulphur may be present as impurities. The nickel may also contain about 1 percent of cobalt.

I claim:

1. A nickel-chromium-iron alloy containing substantially 35 percent nickel, substantially 15 percent chromium, substantially .03 percent calcium, substantially .05 percent zirconium, balance iron.

2. An electric resistance element consisting es- 'sentially of substantially 35 percent nickel, substantially 15 percent chromium, substantially .03 percent calcium, substantially .05 percent zir conium, balance iron.

3. A nickel-chromium-iron alloy containing substantially 35% nickel, substantially 15% chromium, .01 to 20% calcium, .01 to 50% zirccnium, balance iron. v

4-. A nickel-chromium-iron alloy containing substantially 35% nickel, substantially 15% chromium, substantially .03% calcium, substantlally .93 to 25% zirconium, balance ir'cn.

JAMES M. mm. 

